I was talking to the guys at maxamps.com (a bunch of nice guys who were very helpful) and they suggested a way to balance a stack of LiPo cells that sounded good to me and to which I've added to a bit below. Since I'm pretty new to all this and am not a battery engineer, I wanted to check first to see if anyone who actually did know what they were talking about had improvements or other comments:

Wire the battery so that each cell's negative and positive terminal come to a sperate pin on a tap connector (6 pins for a 3-cell battery). Then set up some prebuilt jumper blocks such that when flying the pack, the cells are wired in series with heavy guage wires to the ESC connector. Have another set of jumpers so that the cells are wired in parallel for charging. In this configuration, when not under charge, the cells would be self balancing as all three cells would dischage/charge into each other until at identical voltages.

Other than the extra few grams for the taps and jumpers, are there any disadvangages to this? Will the cells actually self-balance when wired in parallel?

wevets

Red Scholefield

08-13-2005, 09:11 PM

All you have to do is bring out 2 more wires for the center cell. In this way you can measure the voltage of each occasionally and if they are out by more than 10 mv you can charge them individually by picking up the right combination on wires.

The cells probably would take sometime to balance themselves if they were significantly out of balance when connected in parallel.

The battery mfgs have started putting taps in their lipo packs. Last set of Tanics I bought last month has them. I also see other mfgs advertising their style or system to balance the packs. So I would say we have a pretty good choice of which way to go.

wevets

08-26-2005, 11:53 PM

The taps being put into LiPos today let you charge each cell individually, but don't allow you to charge the whole battery as a set of cells in parallel. To do this, it would be necessary to bring out each side of each cell out on an individual pin and would require the cells be connected, using a different header, in series (to fly) or in parallel (to charge).

The way taps are currently being made availble, the cells are wired permanently in series with taps being brought out at the connections between cells in the series stack. This way, you can measure the voltage across any individual cell and charge it individually, but you can't put all the cells in parallel and charge them that way or let them self-balance.

Wevets

Lazyflier

08-27-2005, 04:06 AM

The taps being put into LiPos today let you charge each cell individually, but don't allow you to charge the whole battery as a set of cells in parallel. To do this, it would be necessary to bring out each side of each cell out on an individual pin and would require the cells be connected, using a different header, in series (to fly) or in parallel (to charge).

The way taps are currently being made availble, the cells are wired permanently in series with taps being brought out at the connections between cells in the series stack. This way, you can measure the voltage across any individual cell and charge it individually, but you can't put all the cells in parallel and charge them that way or let them self-balance.

Wevets

Let it be known that I don't represent Tanic. I just search the web. I found this interesting solution to balancing a pack for 35 bucks or close to it. Looks like it would save a lot of wiring to try an unproven theory.
I have not found any information yet that states the cells self balance if charged in parallel.
I have seen information that it's mostly the larger packs that have a higher chance to go out of balance so I really don't worry about it with my 2s and 3s packs. after many cycles of charging my tanics no unbalance when I check them
http://www.tanicpacks.com/catalog/product_info.php?cPath=57&products_id=484

$Order two chargers for a 2S pack
order 3 chargers for a 3S pack
order 4 chargers for a 4S pack etc.
All chargers use standard 110VAC, [B]NO POWER SUPPY NEEDED!!!!!
a power bar may be necessary.
http://www.tanicpacks.com/catalog/images/pixel_trans.gifhttp://www.tanicpacks.com/catalog/images/balance-charger.gif
Click to enlarge (javascript:popupWindow('http://www.tanicpacks.com/catalog/popup_image.php?pID=484')) images/balance-charger.gif
Click to enlarge (http://www.tanicpacks.com/catalog/images/balance-charger.gif)These are the simpliest 1 cell chargers we have ever seen. They are designed to charge cell phone batteries. We have found that it is possible to use as many as necessary to charge your TANIC PACK through the taps, ALL AT THE SAME TIME. No more worrying about over voltage into a cell, the voltage will never exceed 4.25 volts and therefore no danger of pack ignition!!!! 100% balanced packs every time.
They are not fast though 150mah ,but will perfectly charge/ balance your pack every time. The charger includes the adaptor that will fit your "TANIC TAP" ( male JST) and as an option we have an adaptor for aligator clips for other brand lipo packs
Order two chargers for a 2S pack
order 3 chargers for a 3S pack
order 4 chargers for a 4S pack etc.
All chargers use standard 110VAC, NO POWER SUPPY NEEDED!!!!!
a power bar may be necessary.